This invention relates to catheters that can by steered by external controls. More particularly the invention relates to such catheters that can assume three dimensional curves.
Modern medical procedures rely ever more upon minimally invasive access to organs and tissues of a patient, frequently via body lumens such as veins or arteries. A common feature of most such procedures is that a medical device may be carried at the distal tip of a catheter, or may be inserted to the tip of a steerable assembly, to a desired location in the body of a patient, where it may be activated. For example, one or more electrodes may be provided at the distal end of a catheter for purposes of tissue ablation; inflatable balloons may be provided for purposes of vessel expansion, or for separating tissue layers to create a space to perform a further procedure; blades or rotating burrs may be provided for purposes of clearing a blocked lumen; or, needles may be provided for injecting agents into body tissue. Various steering mechanisms for catheters carrying such devices have heretofore been developed and used.
Physicians have used a number of different catheters and techniques, each of which provides a different characteristic. Some catheters have been developed that allow a physician to move a distal end of a catheter in any direction, thereby permitting the physician to steer a tool to the desired location. In some circumstances, this is a useful advantage, in that it allows a physician freedom to move a catheter tip in a direction that could not be anticipated beforehand.
However, problems persist in the art of steerable catheters in applications such as the foregoing. In certain applications, a physician may be confronted with an extremely tortuous luminal passageway in the body of a patient to navigate, but where the general shape of the tortuous passageway can be predicted beforehand. An example is in the case of cardiac surgery, such as mitral valve repair. During mitral valve repair, the process will typically comprise accessing a patient's vasculature at a location remote from the heart such as the iliac artery in the thigh, advancing an interventional tool through the vasculature to a ventricle and/or atrium in the heart, and engaging the tool for its designed purpose. By engaging the tool, the tissue structure of the valve may be modified in a manner that reduces valve leakage or regurgitation during ventricular systole. Typically, once the interventional tool has been advanced all the way from the remote access point to the heart using a steering feature that has been provided, the physician must position the tool in the heart in such a manner that allows the physician to manipulate the catheter in relation to the target tissue. At this point, a problem may arise in that the steerable portion of the catheter at the distal end does not permit the physician enough control over the tool attached to the distal end of the catheter. This phenomenon may arise because the steerable portion may have the capability of changing its position under the application of slight external forces such as may naturally occur within the patient's anatomy. Thus, just when a physician believes the tip of the catheter is in the correct place to conduct the intended procedure, the tip of the catheter may change its position without the physician applying any additional force via pullwires such as may be used to steer the catheter, and this effect may thereby disrupt the procedure until the tip is repositioned. The problem may persist even when, with reference to FIGS. 18 and 19, a steerable assembly is formed, according to methods known in the art, from a long tube 700 with slits 702 formed in the wall of the tube with the intention of ultimately providing a pre-shaped configuration to the tube, as exemplified in FIG. 19. The problem here arises when opposing pullwires, for pulling the distal tip of the tube from one side to the other, are freely extended up the bore of the tube and are connected to opposing sides at the distal tip of the tube. Yet a further problem may tend to arise with the kind of steerable assembly disclosed in FIGS. 18 and 19, for, although the slits in the tube wall may enable the tube to bend, the radius of curvature of the bend may not be sufficiently small to satisfy the desired shape of the assembly.
Thus there is a need in the art for a catheter that addresses the shortcomings of the prior art. The present inventive concept aims at reducing at least some of the shortcomings of the prior art.